Body limb movement limiter

ABSTRACT

A body limb movement limiter restrains the movement of a person&#39;s arm so as to protect the person&#39;s shoulder or restrains the movement of a person&#39;s lower leg with respect to the upper leg so as to protect the person&#39;s knee. The device uses a housing having a reel disposed therein with a tether attached thereto and a shear thickening non-Newtonian fluid disposed within the housing so that the fluid acts on the reel during a payout procedure of the tether. The housing is attached to a strap secured about the torso of the person while the free end of the tether is secured about the person&#39;s arm. Alternately, a pair of arms are pivotally secured to each other within a housing having the non-Newtonian fluid therein for limiting movement of one arm with respect to the other.

This application is a cip of U.S. patent application Ser. No.09/992,611, filed on Nov. 19, 2001, now abandoned, which itself claimsthe benefit of U.S. Provisional Patent Application 60/249,312, filed onNov. 17, 2000.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a body limb movement limiter that usesa non-Newtonian fluid so as to prevent sudden rapid movement of aperson's arm or leg, or other joint, thereby preventing injury to theperson's injury-recovering joint.

2. Background of the Prior Art

In recovering from an injury to the shoulder, knee, or other joint, withor without surgery to the joint, slow and gradual use of the affectedarea is desired in order to build strength and prevent shortening of theaffected tendon or ligament. If the joint is subjected to sudden rapidforces the healing process to the affected area can be compromisedresulting in a slowing of the healing of the affected area, reinjury, orfurther damage to the affected area which can result in the need foradditional medical intervention. This not only results in furtherdiscomfort to the patient but slows the overall healing and recoverytime.

Devices have been proposed that help limit movement of a person's jointsuch as the shoulder, knee, elbow, ankle, hip, etc., so as to preventthe patient from subjecting the joint to sudden rapid acceleration andconsequent forces on the affected area. Such devices help prevent theattendant damage that can result from such rapid acceleration and workwith varying degrees of efficiency.

The problem with the movement limiting devices found in the art is thatsuch devices, being linear in their deceleration capacity, limit thenormal and desired movements of a user of such devices. Such devicesfail to discriminate between a desired normal movement associated withthe joint and an undesired rapid movement than can cause damage to theuser. These devices tend to make many normal movements, such as walkingor carrying groceries relatively uncomfortable. While such discomfortsmay be an acceptable tradeoff to some, for the benefit of minimizingdamage resulting from undesired rapid acceleration, these discomfortsare less than ideal.

Other prior art devices will allow normal movement associated with ashoulder or a knee to a point and once that point is surpassed, abraking action is applied. While these devices will prevent much of thedamage associated with full rapid acceleration of the affected area, thesudden braking action can cause a jerking force on the shoulder or knee,which can result in undue discomfort or some amount of damage to thetendons or ligaments thereat.

Therefore, there exists a need in the art for a device that will preventrapid movement associated with a person's shoulder or knee or otherjoint. Such a device will allow the user to perform normal desirablefunctions without undue discomfort, yet will prevent sudden rapidacceleration of a person's limb, resulting in pain, reinjury or damageto the person's joint. The deceleration provided by such a device mustbe gradual so as not to exert a jerking force onto the user's affectedarea. Ideally, such a device must be of relatively simple design andconstruction and must be relatively easy to don and use.

SUMMARY OF THE INVENTION

The body limb movement limiter of the present invention addresses theaforementioned needs in the art. The body limb movement limiter is wornby a user and helps prevent the sudden rapid movement of a person's limbin order to protect a recuperating joint associated with the limb. Thedeceleration provided by the device is gradual and corresponds to theattempted force exertion of the limb which the device is decelerating.The device does not impose a sudden jerking force on the targeted limb.The body limb movement limiter of the present invention is of relativelysimple design and construction and is relatively easy to don and use.

The present invention relies on the properties of shear thickening ordilatant non-Newtonian fluid for smooth and gradual braking action. Inan ideally viscous system, a fluid exhibits Newtonian flow behaviorwherein a linear relationship exists between shear stress and shear ratewhere the coefficient of viscosity is the constant of proportionality.The viscosity of the fluid is constant over the measured range of shearrates. On the other hand, a non-Newtonian fluid exhibits nonlinearcharacteristics, which can be described by several different types ofbehavior.

One of the three most common types of non-Newtonian fluid behavior isshear thinning or pseudoplastic. With increasing shear rate, theviscosity of the fluid decreases. This is the most common type ofnon-Newtonian fluid behavior. Pseudoplastic behavior is a highlydesirable trait for many materials including inks, extrusion materials,and paints. For example, modern paints exhibit high viscosity at restwhen a brush is dipped into the paint, thereby allowing the brush topick up and carry a significant amount of the paint. However, as theshear rate increases, due to brushing, the viscosity is decreasedallowing a thin, even layer of paint to be applied to the surface beingbrushed. One major class of chemicals that exhibits pseudoplasticbehavior is the dimethylsiloxanes and other silicone chemicals as shownin the viscosity vs. shear rate graph for a manufacturer of suchsilicones, United Chemical Technologies, of Bristol, Pa.—http://www.unitedchem.com/PDF/petrarch%205.pdf at page 237.

Another common type of non-Newtonian fluid behavior is known as shearthickening or dilatant. With increasing shear rate, the viscosity of thefluid increases. This type of behavior is uncommon, but is findingincreased usage in various applications. The most common example of ashear thickening or dilatant non-Newtonian fluid is a concentratedmixture of cornstarch and water. In most industrial processes, shearthickening is undesirable as it tends to cause equipment that ishandling materials with high particulate loading to freeze up.

A third common, albeit the least common of the three major types, isknown as Bingham plasticity. At low shear rates, the material behaves asa solid. Above a “yield stress,” the material is essential Newtonian.One of the most common examples of this type of behavior is toothpaste.

The body limb movement limiter of the present invention, as applied to aperson suffering a shoulder or knee injury, is comprised of a housinghaving an opening and a reel rotatably disposed therein. A tether havinga first end is attached to the reel and a second end located external ofthe opening, the tether wound about the reel. A shear thickening ordilatant non-Newtonian fluid is disposed within the housing and actsupon the reel during unwinding of the reel. A first strap is attached tothe housing and is adapted to be secured about the torso of a person.The non-Newtonian fluid acts as a gradual brake due to the fact that theviscosity of the fluid increases as the force applied to a member withinthe fluid increases. A first closure means, such as cooperating hook andloop material, is provided for securing the ends of the first straptogether. A second strap is attached to the second end of the tether andis adapted to be secured about an arm of the person. A second closuremeans, such as cooperating hook and loop material, is provided forsecuring the ends of the second strap together. The tether is comprisedof a first section removably secured to a second section. The housing iscomprised of a first chamber and a second chamber fluidly sealed fromthe first chamber and such that the reel is disposed within the firstchamber and a rotor is disposed within the second chamber such that therotor is mechanically connected to the reel such that rotation of thereel causes rotation of the rotor and wherein the shear thickeningnon-Newtonian fluid is disposed within the second chamber. Alternately,the body limb movement limiter can be comprised of a first housing and afirst arm having a first end disposed within the first housing and asecond end. A second arm having a third end is pivotally attached to thefirst end of the first arm, and has a fourth end. A shear thickeningnon-Newtonian fluid is disposed within the first housing and acts on thefirst arm during movement of the first arm with respect to the secondarm. A second housing has a third arm having a fifth end disposed withinthe second housing and a sixth end. A fourth arm having a seventh end ispivotally attached to the fifth end of the third arm, and has an eightend. A non-Newtonian fluid is also disposed within the second housingand acts on the third arm during movement of the third arm with respectto the fourth arm. A first stabilizer connects the first housing withthe second housing. The first housing is comprised of a first chamberand a second chamber fluidly sealed from the first chamber and such thatthe first arm is disposed within the first chamber and a first rotor isdisposed within the second chamber such that the first rotor ismechanically connected to the first arm such that movement of the firstarm causes movement of the first rotor and wherein the non-Newtonianfluid is disposed within the second chamber and the second housing iscomprised of a third chamber and a fourth chamber fluidly sealed fromthe third chamber and such that the third arm is disposed within thethird chamber and a second rotor is disposed within the fourth chambersuch that the second rotor is mechanically connected to the third armsuch that movement of the third arm causes movement of the second rotorand wherein the non-Newtonian fluid is disposed within the fourthchamber. A first strap connects the first arm with the third arm while asecond strap connects the second arm with the fourth arm. A secondstabilizer connects the second arm with the fourth arm.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a is a perspective view of the body limb movement limiter forlimiting movement of the upper arm region.

FIG. 1 b is a perspective view of the body limb movement limiter forlimiting movement of the lower arm region.

FIG. 2 a is a perspective view of the body limb movement limiter forlimiting movement of the upper arm region wherein the body strap and thearm band are both closed.

FIG. 2 b is a perspective view of the body limb movement limiter forlimiting movement of the lower arm region wherein the body strap and thearm band are both closed.

FIG. 3 is an environmental view of the body limb movement limitershowing the embodiments of FIGS. 1 a and 1 b secured to a user.

FIG. 4 is an elevation view of the limiter housing.

FIG. 5 is an elevation view of the limiter housing having the coverremoved.

FIG. 6 is a close-up view of the two tether sections connected togetherwithin the limiter housing.

FIG. 7 is a sectioned view of the housing.

FIG. 8 is a perspective view of the body limb movement limiter forlimiting movement of the lower leg region.

FIG. 9 is an environmental view of the body limb movement limiter ofFIG. 8 secured to a user.

Similar reference numerals refer to similar parts throughout the severalviews of the drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings, it is seen that the body limb movementlimiter of the present invention, generally denoted by reference numeral10, is comprised of a limiter housing 12, having a cover 14 for accessto the interior thereof, the housing 12 being attached to a strap 16dimensioned to either fit about the chest of a user, as seen in FIGS. 1a and 2 a or the strap 16 is dimensioned to fit about the waist of auser, as seen in FIGS. 1 b and 2 b.

A first chamber 18 and a second chamber 20 are each located within thehousing 12. A take-up reel 22 is rotatably disposed within the housing12 and passes through the two chambers 18 and 20. A tether 24 has afirst end that is connected to the take-up reel 22 and has a second endthat is located exterior of the housing 12 and passes through guides 26located at the opening of the housing 12. As seen, the tether 24 may becomprised of a first section 24 a and a second section 24 b such that aconnector 28 of any appropriate design connects the two sections 24 aand 24 b. The take-up reel 22 has an automatic take-up mechanism (notillustrated) of any design commonly found in the art such that wheneverthe tether 24 is unwound from the take-up reel 22, the take-up mechanismcauses the take-up reel 22 to automatically rewind the tether 24 ontothe take-up reel 22. Disposed within the second chamber 20, a rotor 30is also connected to the take-up reel 22 and rotates with the rotationof the take-up reel 22. A non-Newtonian fluid 32 is also disposed withinthe second chamber 20 and substantially fills the second chamber 20. Apair of O-rings 34 prevents the non-Newtonian fluid 32 from escapingfrom the second chamber 20. The non-Newtonian fluids of interest forthis application are those which increase in viscosity with increasingshear forces. A band 36 is connected to the free end of the tether 24.The band 36 is dimensioned to fit about a user's upper arm as seen inFIGS. 1 a, 2 a, and 3, or the band 36 is dimensioned to fit about theuser's lower arm as seen in FIGS. 1 b, 2 b, and 3. A first closuremechanism 38 secures the two ends of the band together. The firstclosure mechanism 38 can be of any appropriate design such as theillustrated cooperating hook and loop material.

In use, the strap 16 is fit either about the user's chest or about theuser's waist. The strap 16 is secured in place by providing a secondclosure mechanism 40. The second closure mechanism 40 can be of anyappropriate design such as the illustrated cooperating hook and loopmaterial. The band 36 is placed around the appropriate portion of theuser's arm—either about the user's upper arm if the strap 16 is placedaround the user's chest, or about the user's lower arm if the strap 16is placed about the user's waist. For use together, a wide strap withover-the shoulder stabilizing straps accommodates both mechanisms.

As the fluid 32 disposed within the second chamber 20 is a shearthickening non-Newtonian fluid, the more force applied to the rotor 30,the more viscous the fluid 32 becomes and the more friction the fluid 32exerts on the rotor 30 thereby tending to dampen the rotation of therotor 30. Therefore, if the user moves his arm away from his body in aslow fashion, the take-up reel 22 and the connected rotor 30 will berotated, via the tether 24 connected to the take-up reel 22, relativelyslowly, and the frictional damping placed on the rotor 30 by the fluid32 will be relatively small. However, if the user moves his arm suddenlyand quickly away from his body, the user's pull on the take-up reel 22and the rotor 30 will be relatively strong. As the rotor 30 is disposedwithin the fluid 32, the increased force exerted on the rotor 30 resultsin more frictional dampening by the fluid 32 against the rotor 30. Thisresults in a braking action on the take-up reel 22 preventing the userfrom the desired quick movement of his arm. The braking action will begradual so as to prevent a jerk on the take-up reel 22 and thus on theuser's arm. Therefore, a user who is suffering from an arm or shoulderinjury or other condition will be prevented from rapid high accelerationmovements of the arm, thereby tending to eliminate injury to the healingtendons and ligaments that can be occasioned from such a sudden movementof the arm. As the braking action is soft and gradual, the arm will notbe jerked to a stop and thus injury from such a jerk stop will beavoided.

The take-up of the tether 24 upon the take-up reel 22 will be controlledby the take-up mechanism. The take-up mechanism is designed so as not toperform the take-up operation too fast. Additionally, the user tends tomake the return movement of his arm back to his body much moreconsciously, therefore, the gradual braking action provided by thedevice 10 is not necessary for the return of the arm.

As the tether 24 is in two sections 24 a and 24 b, the two sections canbe made from separate material. Additionally, whenever the secondsection 24 b becomes worn or otherwise needs to be replaced, the secondsection 24 b can be detached from the first section 24 a and a newsection reattached external of the housing 12, thereby eliminating theneed to disassemble the device 10 in order to effect a second section 24b replacement. The maximum pay out of the tether 24 from the take-upreel 22 is a human arm's length which is the length as measured betweenthe strap 16 and the band 36 when the arm of the user that has the band36 thereon is fully extended in a direction that is opposite the housing12.

As seen in FIGS. 8 and 9, the body limb movement limiter 10′ of thepresent invention can also be used to prevent sudden and quick movementsof the lower leg of the user. Such a device 10′ is comprised of a brace42 that has a pair of upper arms 44 and a pair of lower arms 46. A pairof plates 48 is provided and is connected together by a first stabilizer50. Located on each of the plates 48 is a housing 12′ such that one ofthe upper arms 44 is hingedly connected to a corresponding lower arm 46within one of the housings 12′ and the other upper arm 44, lower arm 46pair is hingedly connected to each other within the other housing 12′.The lower arm 46 is connected to a rotor (not illustrated), the rotordisposed within a chamber within the housing, the chamber having a shearthickening non-Newtonian fluid substantially filling the chamber. Therotor moves in lockstep with movement of the lower arm 46 to which it isattached. Therefore, the faster the attempted acceleration of the lowerarm 46, —corresponding to rapid attempted acceleration of the lower legof the user—the more viscous the non-Newtonian fluid becomes and themore frictional dampening placed onto the rotor by the fluid, resultingin gradual braking of the lower arm 46 and thus the lower leg of theuser. This arrangement prevents rapid acceleration of both forward lowerleg movement and rearward leg movement. The brace 42 is placed onto theuser such that a second stabilizer 52 that connects the two upper arms44, rests on the upper surface of the user's thigh. A first strap 54 iswrapped around the thigh and the first strap 54 is connected to itselfby an appropriate closure mechanism 56 such as the illustrated hook andloop material. A second strap 58 is wrapped around the lower leg of theuser and the second strap 58 is secured to itself by an appropriateclosure mechanism 60 such as the illustrated hook and loop material. Ifdesired, some or all components of the brace 42 are padded for increaseduser comfort.

The use of relatively small tether payout used with the presentinvention 10 can be modified for use as a vehicular seat belt payoutsystem wherein the seat belt strap acts as the tether and is wound aboutthe take-up reel which is connected to a rotor disposed within the shearthickening non-Newtonian fluid. In such an embodiment, at relatively lowshear rates, such as when a person buckled in by the seat belts movesabout—to change the stereo settings for example—the take-up reel paysout the seat belt strap in relatively normal fashion. However, at highshear rates, such as when the seat belt is suddenly and violently jerkedduring a vehicular crash, the viscosity of the shear thickeningnon-Newtonian fluid increases causing a gradual breaking on the seatbelt strap and preventing the occupant from hitting the windshield ordashboard while, due to the gradual braking action of the non-Newtonianfluid, also preventing a serious impact injury caused by a complete andsudden jerk stop of the strap upon the person's upper torso region.

While the preferred embodiment employs a shear thickening non-Newtonianfluid to produce a body limb movement limiter that requires no externalpower source, other means of preventing the forces generated by rapidacceleration can be employed, such as a combination of accelerationsensing and “soft” or dampened braking achievable by electrically drivenclamps or electrically or magnetically modified fluid viscosity.

While the invention has been particularly shown and described withreference to embodiments thereof, it will be appreciated by thoseskilled in the art that various changes in form and detail may be madewithout departing from the spirit and scope of the invention.

1. A method of limiting the movement of a person's limb comprising thesteps of: providing a housing having an opening and a reel rotatablydisposed therein and securing the housing to the person; providing atether having a first end and a second end; attaching the first end ofthe tether to the reel, winding the tether about the reel, and securingthe second end of the tether to the person's limb; and placing a shearthickening non-Newtonian fluid within the housing for acting on the reelwhenever the tether pays out from the housing and such that the pay outof the tether from the housing is decelerated.
 2. The method as in claim1 further comprising the steps of: wherein the step of securing thehousing to the person comprises providing a first strap and attachingthe housing to the first strap; and securing the first strap about thetorso of the person.
 3. The method as in claim 2 further comprising aclosure means for securing the ends of the first strap together.
 4. Themethod as in claim 2 further comprising the steps of providing a secondstrap and attaching the second end of the tether; and securing thetether to the limb via the second strap.
 5. The method as in claim 4further comprising a closure means for securing the ends of the secondstrap together.
 6. The method as in claim 4 wherein the tether iscomprised of a first section removably secured to a second section. 7.The method as in claim 1 wherein the housing is comprised of a firstchamber and a second chamber fluidly sealed from the first chamber andsuch that the reel is disposed within the first chamber and a rotor isdisposed within the second chamber such that the rotor is mechanicallyconnected to the reel such that rotation of the reel causes rotation ofthe rotor and wherein the shear thickening non-Newtonian fluid isdisposed within the second chamber.